Let a device hand a file to the server for hashing and validation

frontend/opfs.js

@@ -108,6 +108,17 @@
       }
     },
 
+    // The saved File itself (disk-backed, not read into memory) — used as an
+    // upload body by P2P intake. null when not saved.
+    async getFileObject(videoId) {
+      try {
+        const found = await findHandle(videoId);
+        return found ? await found[0].getFile() : null;
+      } catch {
+        return null;
+      }
+    },
+
     // Bytes [offset, offset+length) of a saved video — answers the server's
     // P2P range challenges (p2p-client.js). null when the file is missing.
     async readRange(videoId, offset, length) {